Recently, I answered a question "What metals aren't dissolved in/attacked by aqua regia?" in which I finally concluded "ruthenium is resistant to aqua regia in any form at any concentration of acid".Fellow answerer @Linear Christmas also supported my statement

However, in my answer, I pointed out that something is not right. In the blockquote I wrote:

Ruthenium can be dissolved in aqua regia only when in the presence of oxygen (Why? will be asked in a separate question)

It is written that ruthenium can only be attacked in aqua regia in the presence of oxygen. And for this statement, this question is asked. This statement can also be found in the wikipedia article of noble metal.

In the wikipedia article of ruthenium it is clearly written that:

Ruthenium (...) is not attacked by acids (even aqua regia)

Even in the handbook, it is written that (statement can be found in my answer):

Ruthenium is by far the most chemically resistant of the noble metal, unattacked either in hot or cold aqua regia.

Also this video by Nurdrage shows that ruthenium is invulnerable to aqua regia or any kind of acid.

However in this google book, it is written:

Pure ruthenium powder or sponge is not appreciable attacked by hot, single or mixed mineral acid(aqua regia).

Why it is written "not appreciable attacked"? Maybe it should have wrote invulnerable or resistant. I am assuming that the corrosion rate is not appreciable/very slow i.e. corrosion is too slow to get noticed by naked eye.

Is my assumption correct? Can ruthenium be attacked in aqua regia only in presence of oxygen? Why wikipedia wrote that statement regardless of the fact that ruthenium is resistant to aqua regia in any form at any concentration of acid? I have not found any evidence that shows ruthenium is vulnerable to aqua regia.


1 Answer 1


Page 807 of A Textbook of Inorganic Chemistry says that iridium, rhodium. and ruthenium are "almost unaffected" by aqua regia. So "completely invulnerable" = no, but "resistant" = definitely yes.

  • 3
    $\begingroup$ Can you elaborate a little? $\endgroup$ Commented Jan 30, 2017 at 6:00

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